If you have always wanted to have your thoughts preserved for posterity, your time has come.

You have two years in which to compose an essay of no more than four, foolscap pages (roughly 2,000 words), which will be placed in orbit around the Earth for 50,000 years.

Together with similar messages to the distant future submitted by people from all over the world, your thoughts will be engraved on glass discs and installed in a small satellite which will be shot into orbit in two years' time.

The satellite, to be carried free by an Ariane-5 rocket of the European Space Agency, will include information of possible interest to our distant descendants, or anyone else who happens to be around in 52,000AD. There will be a digital encyclopedia of the sum of human knowledge in 2004, a frieze of human faces from every country on earth and four small, golden spheres containing a drop of human blood, a drop of seawater, a grain of soil and a bubble of air.

The KEO project – dreamed up by a French "scientific artist", Jean-Marc Philippe – is intended to record forever the state of humanity in the early 21st century and present the findings as an "archaeological gift" to the future. The satellite will be placed in an orbit which should bring it back to Earth in 500 centuries.

The idea has the support of aerospace companies, the French foreign ministry, the European Space Agency and Unesco. Launching the project at a conference on top of the Grande Arche de la Défense, just outside Paris, Philippe invited allcomers to "visit your own thoughts".

Contributions may be sent by e-mail to www.keo.org or by post to KEO, BP100, 75262 Paris Cedex 06, France.